1. Field of the Invention
This invention relates to polymeric dispersant additives for lubricants and hydrocarbon fuels. When of high molecular weight, the additives are also useful as viscosity-index improvers for lubricants. More particularly, this invention relates to copolymers, having a degree of crystallinity of 3 to 25 weight percent, as determined by X-ray or differential thermal analyses, comprising from about 68 to 80 mole percent of ethylene and one or more C.sub.3 to C.sub.8 alpha-olefins, usually propylene, which have been mechanically degraded as by intensive milling at elevated temperature, usually in the absence of a solvent or fluxing medium, and in the presence of air or oxygen-containing gas to form an oxygenated degraded polymer which is reacted with an amine compound to form an aminated oxy-degraded polymeric reaction product.
2. Description of the Prior Art
A variety of polymeric materials which incorporate nitrogen have been described in U.S. and foreign patents as dispersants for fuels and lubricants, and as viscosity index improvers for lubricants. For example:
U.S. Pat. No. 3,404,091 grafts polar monomers, such as acrylonitrile onto hydroperoxidized copolymers of ethylene and propylene.
U.S. Pat. No. 3,404,092 reacts hydroxylated ethylene-propylene copolymers with isocyanates.
U.S. Pat. No. 3,687,849 grafts various unsaturated monomers onto a degraded, hydroperoxidized, interpolymer of ethylene and propylene.
U.S. Pat. No. 3,769,216 shows an atactic (i.e., non-crystalline) copolymer of ethylene and propylene containing from 45 to 65 mole percent of ethylene, mechanically degraded in the presence of oxygen, followed by reaction with a polyamine.
U.S. Pat. No. 3,785,980 discloses the reaction product of an amine with a hydroperoxidized atactic copolymer of ethylene and propylene containing from 45 to 65 mole percent of ethylene.
British Pat. No. 1,172,818 describes the preparation of lube oil additives by the condensation of an amine with an oxidized, e.g., ozonized, polymer.